The testimony by Prof. Gert Saayman, who performed the autopsy on Reeva Steenkamp's body, was so graphic that it was not broadcast or reported live on social media by journalists under an order from Judge Thokozile Masipa.
Saayman methodically listed the extent of the three main gunshot wounds Steenkamp suffered on Valentine's Day last year when she was shot by the double-amputee runner in the right side of the head, the right hip and the right arm through a toilet cubicle door.
The pathologist said Steenkamp, 29, was hit by special Black Talon bullets and that the head shot from Pistorius' 9 mm pistol was probably almost instantly fatal, causing brain damage and multiple fractures to her skull.
Bent over while sitting on a wooden bench, Pistorius vomited when Saayman reached his right hand up toward the right side of his own head to show the entrance and exit wounds in Steenkamp's skull.
Masipa briefly halted the testimony to ask chief defense lawyer Barry Roux to attend to his client. The judge later asked whether Pistorius was able to understand the proceedings as he sat with hands clasped over his ears, his body heaving.
"Is your client fine?" the judge asked Roux.
Roux replied: "It's not going to be fine."
Roux said Pistorius' reaction was not going to change. A dark bucket with a handle was placed at his feet.
Pistorius vomited at least two other times and cried. He is charged with premeditated murder for killing Steenkamp and could face up to life in prison if convicted. The prosecution contends the shooting followed a loud argument between the couple. The defense maintains that he shot her by mistake, thinking she was an intruder.
Through the sounds of Pistorius retching in the dock, the pathologist testified that he was able to identify the ammunition from a bullet fragment lodged at the bottom of Steenkamp's skull. The bullets were designed to expand on impact and cause severe damage.
The hip and arm wounds were also severe, and the right arm was broken, the pathologist said, adding that any of the three gunshot wounds in isolation could have been fatal.
Saayman stood through his testimony to indicate the location of Steenkamp's bullet wounds by touching his hand to his own head, arm and hip. He noted that Steenkamp also had a wound on her left hand, possibly from a bullet, and described abrasions and smaller injuries caused by splinters, which he said were consistent with bullets fired through a wooden object.
Away from the courthouse, JC de Klerk, a forensic ballistic specialist who used to work for the South African police, agreed with Saayman that the headshot likely killed Steenkamp immediately.
"If the doctor found a Black Talon bullet inside her head ... she would have died, I would say, not in seconds but in milliseconds," de Klerk told The Associated Press in a telephone interview.
De Klerk said the bullets were rare in South Africa and designed to cause "excessive wounds."
The detailed evidence regarding the injuries is important because, for one, Pistorius has claimed that Steenkamp was slumped over but alive when he eventually reached her after shooting her in error thinking she was a dangerous intruder.
That appears unlikely given Saayman's testimony, but the pathologist did note that sometimes it takes a little time for a person's heart to stop after a devastating head injury.
But his testimony also could harm the prosecution's claims that Steenkamp screamed during the shooting, unless prosecutors can show that the head shot was the last one to hit her.
Saayman also said that judging by the food contents in her stomach, Steenkamp probably last ate no more than two hours before her death. Steenkamp was shot after 3 a.m., meaning she must have eaten after 1 a.m. That hinted at another possible wrinkle in Pistorius' account because he claims the couple was in the bedroom by 10 p.m.
Pistorius' defense team has indicated it will submit its own autopsy report to support his claim that the killing was a tragic accident.
If convicted on the murder charge, Pistorius, 27, could be sent to prison for at least 25 years before the chance of parole, the minimum time someone must serve if given a life sentence in South Africa. The judge will ultimately deliver the verdict and decide on any sentence. South Africa has no trial by jury.